• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.4
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• pp.599-607
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• 1998

To clarify annual reproductive cycle of Korean dark sleeper, Odontobutis platycephala (Iwata et Jeon), we examined the seasonal changes of gonadosomatic index (GSI), the proportional frequency of oocyte development stages in the ovary and the changes of sex steroid hormone levels in blood from December 1995 to November 1997. In July and August, GSI was 0.35 to 0.72 and most oocytes in the ovary were chromatin-nucleolus stage and perinucleolar stage (proportional frequency: $87\%\~96\%$). In September, GSI was 1.20 $\pm$ 0.12, some oocytes in the ovary were yolk vesifle stage (proportional frequency: $22.8\%$) and vitellogenic stage which appeared very rarely(proportional frequency: $2.2\%$). GSI increased gradually from October and reached 4.59± 0.61 to December. During this period, oocytes of vitellogenic stage increased slightly (proportional frequency in December: $22.1\%$). In January, GSI was 4.32 $\pm$ 0.72 but the proportional frequency of oocytes in vitellogenic stage increased (proportional frequency: $51.2\%$). from February, GSI was increased sharply and reached to 10.51 $\pm$ 1.04 in March, the highest value throughout the year and the proportional frequency of oocytes in vitellogenic stage also reached the highest levels (proportional frequency: $60\%$). From April, GSI was gradually decreased and fell down to 1.11 $\pm$ 0.35 in June. During this period, the proportional frequency of mature oocytes was the highest in April (proportional frequency of mature oocyte stage: $40\%$ in April, $12\%$ May, $5\%$ June) throughout the year, and atretic ovarian follicles were appeared. The blood level of estradiol-17$\beta$ ($E_2$), which stimulates the hepatic synthesis and secretion of vitellogenin, was $0.84{\pm}0.20\;ng/m{\ell}$ in August, and thereafter was not changed until December. from January, it increased sharply and reached the highest level of $ 2.85{\pm}0.35\;ng/m{\ell}$ in March throughout the year, but fell to $0.14{\pm}0.02\;ng/m{\ell}$ in July(P<0.05), 17$\alpha$-hydroxprogesterone(17$\alpha$-OHP) was the peak $13.37{\pm}0.52ng/m{\ell}$ in March, but no significant changes in other period(below $3ng/m{\ell}$, P<0.05). 17$\alpha$, 20$\beta$-dihydroxy-4-pregnen-3-one(17$\alpha$, 20$\beta$-P), which was known as the final maturation inducing hormone in teleost, was $0.74{\pm}0.09ng/m{\ell}$ in April and $0.54{\pm}0.07ng/m{\ell}$ in May, but no significant changes in other period (below $0.26\;ng/m{\ell}$, p<0.05). Taken together these results, the annual reproductive cycle of O. platycephala divided into 4 periods as follows: 1) ripe and spawning period from April to June, main spawning period was from April to May, 2) Resting period from July to August, 3) Growing period from September to December, 4) Maturing period from January to March. Moreover, It was showed that the changes of sex steroid hormone in blood played a important roles in the annual reproductive cycle of O. platycephala.

• Journal of Aquaculture
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• v.12 no.3
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• pp.197-204
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• 1999

Successful produciton of seedlings for marine fish species are highly influenced by the aquisiton of sufficient number of good-quality eggs on required time. human chorionic gonadotropin has been used to induce successful ovulation for the purpose. Rabbitfish, siganus canaliculatus, is inhabited along the coast of Cheju Province and treated valuably for raw fish and fish roasted with seasoning. Female wild-captured rabbitfish (314 to 279 g in body weigth) were injected into intraperitoneal space with human chorionic gonadotropin (HCG) of 5,00,1,000, and 1,500 IU/kg body weight during spawning season of July 14 (trial 1), and July 27 (trial 2). Test fish in trial 1 were injected two times, first on July 14 and second on July 21 with one weekinterval because of no ovulation symptoms, but just one time in trial 2. All females injected both 1,000 and 1,500 IU/kg body weight ovulated in all trials. Among 500 IU/kg injection treatments, just one female ovulated in trial 1 showing 25% of ovulation rate, but none ovulated in trial 2. Ovulation was not occurred in control goups during test period. Time to reach ovulation after injection was 172 to 270 hours in trial 1 and 77 to 132 hours in trial 2, showing shorter as spawning season approached. Generally, ovulation of smaller females were late than that of larger ones. Gonadosomatic index (GSI) and pseudo-gonadosomatic index (Pseudo-GSI) were ranged 22 to 33% and 19 to 28%, respectively. One female spawned 406,200 to 1,032,000 eggs, and obtainable eggs per 100g of body weight were calculated by 130,000 to 190,000. Spawning rates were comparatively high by 96.0 to 98.4%. Rates to reach embryo-formation and hatching were higher in 500 high by 96.0 to 98.4%. Rates to reach embryo-formation and hatching were higher in 500 and 1,000 IU/kg treatments than in 1,500 IU/kg treatment. The result of present study demontrates that HCG treatment during spawning season could become very useful for ovulation of rabbitfish and the suitable dosage was suggested as 1,000 IU/kg of body weight.

• Korean Journal of Environment and Ecology
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• v.35 no.2
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• pp.115-125
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• 2021

This study surveyed the population ecology of Acheilognathus chankaensis (Pisces: Acheilognathinae) in the vicinity of the Churyeongcheon (Stream) and Seomjingang (River) in Jeonbuk, Korea, from February 2006 to May 2007. The survey found the habits mainly in the slow-flowing waters having sand, mud, and gravel bottoms. Age groups estimated by the standard length-frequency distribution of the population indicated that the one-year-olds were 30-46 mm long, the two-year-olds were 47-58 mm long, the three-year-olds were 59-68 mm long, and the four-year-olds were longer than 69 mm. The gonadosomatic index (GSI) and the ratio of ovipositor length/standard length were the highest in March (♀: 12.9%, ♂: 5.0%) and in April (46.3%), respectively. The ratio of mature egg diameters that were 1.6 mm was highest in May (13.2%). The comprehensive analysis of spawning characteristics showed that the spawning season was from March to June with water temperatures in 11.5-22.5℃, and the sex ratio of female:male was 1:1.13. The fecundity in the ovaries and the number of mature eggs were 318±174.5 (50~583) and 220±139.2 (50~406), respectively. The size of the mature eggs was 2.04±0.110 mm on the long axis and 1.55±0.100 mm on the short axis for the study period. Gut contents of A. chankaensis were mainly phytoplankton such as the genera Fragilaria, Synedra, Navicular, Cymbella (Bacillariophyceae), and Cosmarium (Chlorophyceae).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.5
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• pp.413-431
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• 1992

Gonadal development, fertilization and egg development in the maternal body and reproductive cycle of ovoviviparous rockfish, Sebastes inermis, were investigated histologically. Gonadosomatic index(GSI) of male and female were increased from September and reached maximum values in December. In the male, GSI decreased from January, but in the female maintained high values till February and decreased from March. Hepatosomatic index(HSI) was related to GSI conversely. In both sex, HSI increased from February and reached maximum in August as the gonad were degenerating and resting, and began to decrease from September as gonad were glowing. This ovoviviparous rockfish copulates in December. Fertilization with sperms maintained between ovulated oocytes in the ovary occurs in January mainly. Egg development in the ovarian cavity and discharging of hatched preiarva occurs from January to February. The reproductive cycle includes the successive stages: Growing(September), Mature (October-November), Ripe and Fertilization(Decembr-Janua), Egg development and Discharging of hatched larva(January-February), Degeneration and Resting(February-August). According to the frequency distribution of egg diameter and histological observation, the ovoviviparous rockfish discharged the prelarva at a time in a spawning season. The sexual maturation is first attained at 2 ages. All females and males reaches first maturity at body length of 17.1cm and 15.1cm respectively. The mean number of the embryos increased with the increase of the total length of female.

• Journal of Aquaculture
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• v.9 no.1
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• pp.73-81
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• 1996

This study was conducted to study the reproductive cycle in female fusilier, Caesio diagramma by using the histological methods. Histological changes of the ovary were well correlated with the patterns of gonadosomatic index (GSI) and hepatosomatic index (HSI). GSI was increased in April as the value of HSI increase and reached to its maximum in May and June. Oocytes at the chromatin-nucleolus and peri-nucleolus stages were observed in the ovary throughout the year. In April, oocytes containing yolk appeared in ovaries of a few fishes. Most oocytes appearing in May and June belonged to the tertiary yolk stage. Frequency of oocytes appearance at the tertiary yolk stage in May and June was higher than that of the other months. Moreover, the empty follicles and atretic oocytes were observed in the ovaries with many vitellogenic oocytes during these two months. Thereafter, oocytes of the yolk stage disappeared in September. The spawning period of C. diagramma is from the month of April to June, and this species belongs to an asynchronous and multiple spawner.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.5
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• pp.309-315
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• 2005

Changes of sex steroid hormones in the plasma of yellowfin goby, Acanthogobius flavimanus were investigated in relation to the gonadosomatic index (GSI), the hepatosomatic index (HSI) and gonadal development. The GSI in females rose rapidly in November and remained high from December to May $(7.26\pm0.89­6.62\pm0.02)$. The Male's GSI also increased gradually from November and was highest in May $(0.16\pm0.08)$. The HSI in both sexes was in reverse correlation with the GSI, and the HSI was low during the spawning season (February-May). In females, the $estradiol-17{\beta}\;(E_2)$ level increased during vitellogenesis (November and December) and reached its maximum $(8.13\pm2.87 ng/mL)$ at the maturing period, in January. $17{\alpha},\;20{\beta}$-dihydroxy-4-pregnen-3-one$(17{\alpha}20{\beta}OHP)$ gradually increased from October $(0.063{\pm}0.02ng/mL)$ to March $(0.16{\pm}0.02ng/mL)$ and increased rapidly in May. The level of testosterone (T) showed a similar tendency of $E_2$. In males, T increased gradually during spermatogenesis from September to December $(0.14{\pm}0.06­0.26{\pm}0.10ng/mL)$ and peaked in January $(0.36{\pm}0.29 ng/mL)$ when the spermatozoa filled the testis. 11-KT also rose markedly in January and then decreased. On the other hand, $17{\alpha}29{\beta}OHP$ in males did not show any clear tendencies.

• Korean Journal of Ichthyology
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• v.19 no.1
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• pp.8-15
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• 2007

The morphology of gonad and reproductive cycle of ribbed gunnel (Dictyosoma burgeri) were investigated on the basis of histological observation. The specimens were monthly sampled in the coastal waters of Jeju from November 2001 to February 2003. The ovaries and testis of this species are categorized as cystovarian and lobule type, respectively. The gonadosomatic index (GSI) of female increased in November and maintained high values from December to February. The GSI of male was similar to that of female although it was decreased in February. The reproductive cycle can be grouped into the following successive stage in the ovary: growth (October to November), mature (November to February), spawning (January to February), and degenerating and recovery (March to September). And in the testis, the stage observed were: multiplication (August to November), growth (November to January), mature and spawning (November to February), and degenerating and recovery (January to September). The minimum maturation size of D. burgeri was over 15.0 cm and fecundity ranged from 2,194 to 6,581 eggs. The relationship between the fecundity and fish body was calculated in the fecundity (F) equation as: $F=0.4057TL^{3.1425}$ ($R^2=0.7621$) for total length (TL); $F=149.88BW^{0.9579}$ ($R^2=0.7982$) for body weight (BW), respectively. The fecundity was correlated positively with TL and BW. The histological observations of the gonads suggested that major spawning of this species probably occurs between January to February, when low water temperature ($13{\pm}0.3^{\circ}C$) period.

• Korean Journal of Ichthyology
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• v.18 no.3
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• pp.184-192
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• 2006

To investigate reproductive cycle of Tridentiger obscurus in Jeju, total 408 fish were collected in brackish area (May 2004 to August 2005) and total 271 fish were collected in tidal pool (July 2004 to August 2005), respectively. Water temperature ranged $11.0{\sim}21.6^{\circ}C$ in brackish area. Water temperature of tidal pool ($11.1{\sim}24.5^{\circ}C$) in 2005 was similar to that of brackish area although it were highest $30.1{\sim}29.2^{\circ}C$ from July to August in 2004. In brackish area, female gonadosomatic index (GSI) increased in April and maintained high values from May to August. The reproductive cycle can be grouped into the following successive stages in the ovary: immature (November to May), maturing (March to September), ripe and spawning (May to September), and degenerating (July to December). In the tidal pool, female GSI rapidly increased in April and maintained high values until July in 2005. However, it has been low in July 2004 when water temperature was highest. The reproductive cycle can be grouped into the following successive stages in the ovary: immature (August to April), maturing (March to August), ripe and spawning (March to July), and degenerating (July to August 2004 and August 2005). Fecundity of mature female ranged from 1,214 to 12,109 in brackish and ranged from 2,427 to 13,892 in tidal pool area. The fecundity of fish in the tidal pool was significantly higher than that of fish in brackish area. Fecundity was correlated positively with total length and body weigh. Although the large group (> 111 mm total length) in brackish area observed only in spawning season, one in the tidal pool observed from October 2004 until next spawning season. Frequency of the large group was 0 to 12% and 11.4 to 57.9% in brackish area and tidal pool, respectively. These results were indicated that gonadal development of T. obscurus was affected to water temperature and day length.

• Korean Journal of Ichthyology
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• v.32 no.3
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• pp.130-135
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• 2020

Male gonadal development of the yellow catfish, Pseudobagrus fulvidraco, one of the most popular fish species in Korean aquaculture performance, was investigated by histological observation of monthly collected specimens to make comparisons between wild and cultured individuals. Their reproductive cycle was classified into the successive developmental stages as follows: a growing stage (April), a spawning stage (May), a degeneration stage (June to July), and a resting stage (August to October) in the wild and outdoor-cage individuals; a growing stage (April to June), a spawning stage (July to August), a degeneration stage (September), and a resting stage (October) in the indoor-cage ones. Values of gonadosomatic index (GSI) of wild and outdoor cages peaked in May, followed by a sudden decline in August~September and June~August, respectively. In contrast, GSI values of the indoor-cage individuals peaked in September and were followed by a sudden drop. Remarkable seasonal variation in condition factor (CF) was undetectable, peaking in June in the wild-cage individuals and November in the wild ones. Overall, our results suggest that it is suitable to use the male of the outdoor-cage individuals for artificial fertilization and that it is efficient to perform artificial fertilization in May, such as reproductive cycle of wild.

• Korean Journal of Ichthyology
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• v.23 no.3
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• pp.179-186
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• 2011

Slime flounder, Microstomus achne is distributed in the coastal waters of Korea, west sea of Japan, BoHai, Yellow sea and East china sea. They are mainly caught by bottom trawl net during winter, from December to March. Sexual maturation of slime flounder were investigated using samples collected from commercial catch in the southern coast of Korea from November, 2006 to March, 2007. The ovary of the slime flounder is a conical bag in shape and is bilateral structure develops lengthily from the posterior of the abdomen to the end of the anal fin. The testis also is bilateral in structure, usually located in small size in the abdomen. In females, the gonadosomatic index (GSI) were peaked in January (12.46), then decreased rapidly thereafter. Female GSI values plummeted to 2.72 in March just after spawning. Male GSI values were peaked in December (2.46) before in the spawning season, then decreased slowly thereafter. The reproductive cycle would be classified into three successive developmental stages : maturation stage (November to January), ripe and spawning stage (December to February), degenerative and resting stage (February to March). Relationships between the fish sizes in total length (TL) and the number of ovarian eggs (F), the body weights (BW) and the number of ovarian eggs were indicated by the exponential equation respectively: F=29.027TL-767.8 (r$^2$=0.7686), F=0.3998BW+24.288 (r$^2$=0.8919).